YOU SAID:

I think I have ducks in my pants

INTO JAPANESE

私は私のズボンにアヒルがいると思う

BACK INTO ENGLISH

I think there is a duck in my pants

INTO JAPANESE

私はパンツにアヒルがいると思う

BACK INTO ENGLISH

I think ducks are in pants

INTO JAPANESE

私はアヒルがズボンにいると思う

BACK INTO ENGLISH

I think ducks are in pants